Answer:
1.5 billion years ago
Explanation:
Protists are a collection formed up of protozoa, unicellular algae, and fungus forms. We will focus on the being part of this society: the protozoa (proto = first, zoa = beings). Protozoa are the earliest discovered collection of heterotrophic living that utilize and modify complicated meal particles into power. Although protozoans are only made up of a single cell, these organisms control to perform all the necessary responsibilities of life.  The protozoa are split into four principal associations: the ciliates, the flagellates, the heliozoans, and the amoebas.
 
        
                    
             
        
        
        
Explanation:
In a freshwater aquatic ecosystem like a pond, the organisms in the food chain include algae, small animals, insects and their larvae, small fish, big fish and a fish-eating bird or animal
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Answer:
It was previously thought that land plants evolved from stonewort-like algae. However, new research shows that the closest relatives to land plants are actually conjugating green algae such as Spirogyra.
Explanation:The explanation was kinda in the answer. 
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The metric system is a system of weights and measures that was first applied in 1795 in France. Experts everywhere the world use it as the international standard to evidently communicate data. The significance are the following:
•	SIMPLICITY which is the metric system is much simple than the english system because it uses a standard conversion influence for all units. 
•	FAMILIARITY which is almost every nation excluding the united states has accepted the metric system as its official system of weight and measures. 
•	UNIFORMITY which is scientists use the metric system so all experiments are conducted using the same weights and measures. 
•	HISTORY which is the general session on weights and measures formally chosen six metric units to be used as international standards in 1954 and in 1960 and the meter was formally distinct established on the wavelength of light from krypton atoms.
•	TYPES which is the metric system use meters for space, grams for mass, liters for volume and candelas for light.